Intermittent and Fluid Catalytic Reforming of Naphthas HENRY G. McGRATH and LUTHER R. HILL
Downloaded by EAST CAROLINA UNIV on June 19, 2014 | http://pubs.acs.org Publication Date: January 1, 1951 | doi: 10.1021/ba-1951-0005.ch005
The M. W. Kellogg Co., Jersey City 3, N. J.
Hydroforming was the first catalytic naphtha-reforming process to be employed commercially. Eight plants built before and during World War II synthesized nitration grade toluene and aviation gasoline components. Operation is now for motor gasoline and/or aromatics. Continued research and developmentwork have resulted in a fluid hydroforming process offering lower investment and operating costs and improved product distribution. As it is a regenerative process, it is truly continuous and can operate on cracked or virgin naphthas of any boiling range and crude source regardless of sulfur content. Another attribute lies in the very high octane numbers that are attainable.
Twenty-five years ago low quality straight-run naphtha obtained b y simple distillation from crude was used directly as motor gasoline. N o t long thereafter thermal processing in the form of high-pressure high-temperature reforming was used, and i n the middle thirties, other forms of thermal or pyrolytic naphtha upgrading such as naphtha reversion, polyforming, and pyrolysis were introduced. I n 1939 the first catalytic naphtha upgrading process—hydroforming—became a commercial reality, marking a distinct departure from the previous methods, which employed a combination of heat and pressure to effect the desired reaction. Numerous other catalytic processes including catalytic cracking, isomerization, alkylation, and catalytic polymerization were also launched i n the late thirties. The principal reaction i n hydroforming, which is essentially a dehydrogenation process normally using a molybdenaalumina catalyst, is the synthesis of aromatics. Hydroforming is conducted i n the presence of hydrogen, which is derived from the process itself. The large amount of dehydrogenation taking place is the source of the recycled hydrogen. The endothermic heat of reaction, which must be supplied, is almost a direct function of the hydrogen produced. The heat of reaction can be reduced, if desired, b y introduction of olefins—e.g., a thermally cracked naphtha—or b y operation at high pressure. Another dehydrogenation process was introduced before 1944 for converting m e t h y l cyclohexane to toluene over a tungsten-nickel sulfide catalyst. Substantially higher hydrogen partial pressures are employed i n this process than i n hydroforming. Conventional hydroforming is carried out at temperatures of 850° to 1000° F . and pressures of 150 to 300 pounds per square inch gage. Recycle gas rates normally range between 2000 and 4000 cubic feet per barrel of naphtha. Reaction periods of 2 to 12 hours are normally employed i n the fixed-bed units. The commercial feasibility of hydroforming was demonstrated prior to and during World W a r I I b y the construction and successful operation of eight plants, seven of which were designed and built for premium grade motor gasoline and/or toluene and one for 39
In PROGRESS IN PETROLEUM TECHNOLOGY; Advances in Chemistry; American Chemical Society: Washington, DC, 1951.
In PROGRESS IN PETROLEUM TECHNOLOGY; Advances in Chemistry; American Chemical Society: Washington, DC, 1951.
c
Basis reforming plus catalytio polymerization of propylene and butylène 100% C« gasoline Yield, vol. % basis feed Gravity, °API Reid vapor pressure, lb./sq. inch Octane No., C F R M 10-lb. R V P gasoline Yield, vol. % basis feed Extraneous butanes, vol. % basis feed Gravity, °API Octane No., C F R M
Net yields, vol. % basis feed Gasoline (400° F . e.p.) Tar Gasoline inspections Gravity, °API Reid vapor pressure, lb./sq. inch Aniline point, ° F . Octane No., C F R M clear Tar inspections Gravity, °API
8
e
CiH CH« C He Total Gasoline (400° F . e.p. Tar
4
Basis 100% C i recovery Net yields, wt. % basis feed Gas H, + C H
Feed
B
89.7 53.1 5.0 70.7 96.6 7.0 55.9 72.8
90.8 53.2 4.6 69.6 98.4 7.6 57.0 71.9
16.6
70.8
52.2 6.9 94
55.6 9.0 99 70.2 18.4
87.3 2.9
1.9 0.5 2.3 2.1 3.2 10.0 86.4 3.6
1000 2.76 0.0201
89.2 2.7
1.4 0.4 2.1 1.9 3.1 8.9 87.8 3.3
985 2.97 0.0218
A
92.3 6.0 55.7 75.2
86.3 52.4 5.7 73.5
12.7
53.9 10.2 84 74.4
84.8 3.6
2.4 0.6 3.0 2.4 4.0 12.4 83.1 4.5
1000 4.01 0.0199
C
87.4 5.1 53.9 77.6
82.4 51.8 6.3 76.2
11.3
52.5 9.8 78 76.1
80.3 4.7
3.1 0.7 4.0 2.7 4.2 14.7 79.3 6.0
1015 5.26 0.0190
D
(Reaction pressure 1000 pounds per square inch gage)
87.7 5.2 54.3 77.2
82.6 52.0 6.2 75.8
11.5
53.8 11.6 78 76.4
80.9 4.5
2.8 0.6 3.4 2.8 5.4 15.0 79.3 5.7
1015 5.24 0.0190
E
84.6 4.6 54.1 78.5
80.0 51.8 6.6 77.3
10.3
54.1 12.2 70 77.8
78.2 5.4
3.5 0.6 3.9 3.0 5.5 16.5 76.6 6.9
1030 6.22 0.0248
F
80.7 3.7 53.2 80.2
77.1 51.4 7.2 79.3
8.5
54.2 13.2 62 79.5
74.9 5.3
4.2 0.7 4.6 3.7 6.6 19.8 73.3 6.9
1030 7.14 0.0194
G
76.9 2.8 53.3 81.0
74.1 51.8 7.9 80.3
8.0
54.1 13.4 58 80.1
72.1 6.0
5.5 0.6 5.6 3.2 6.7 21.6 70.6 7.8
1045 9.68 0.0216
H
Laboratory Results of Thermal Reforming 2 4 8 / 3 9 6 ° F. East Texas Virgin Heavy Naphtha at 1000 Pounds per Square Inch
Maximum lead temp., • F . Soaking volume factor Coil volume above 900° F . , ou. ft./bbl. naphtha/day
Run No.
Table I.
Downloaded by EAST CAROLINA UNIV on June 19, 2014 | http://pubs.acs.org Publication Date: January 1, 1951 | doi: 10.1021/ba-1951-0005.ch005
η η χ
Ζ
Ό
>
ο
McGRATH AND HILL—CATALYTIC REFORMING OF NAPHTHAS
41
desulfurization of cracked naphtha from a heavy, very sour crude. During W o r l d W a r I I it was necessary to operate largely on a narrow-cut feed stock, preferably a C heart cut or a C - C narrow boiling fraction, to produce toluene and aviation gasoline blending agents. I n this type of operation, one of these plants alone produced more than one half the toluene that went into T N T for the U . S. Armed Forces (6). 7
7
8
90 Fls»d Bed Srdrofarming ρ·1, 2600 SCF/B
Downloaded by EAST CAROLINA UNIV on June 19, 2014 | http://pubs.acs.org Publication Date: January 1, 1951 | doi: 10.1021/ba-1951-0005.ch005
0 85 d -I \ Thermal Reforming Λ Oi Cataljtio Foljmerltatlon 1000 pel
± 80
P l o e
C C / \ / H \ H2 C CH3 H s
HC I HC
3
HC
2
I
—
CH2
•
+
3H
2
X/
H C
2
I H2C
C II CH
c H
2
H C / \HCH H C C
CH3 f \ /
I
HC
\ /
CH S \ / C II
+
CH
3
SH.
^ /
c I
c I CHj
CH3
Dehydrocyclization of paraffins and olefins to aromatics: H C
H2 H2 H2 H2 H2 H2
S\/
I I I I I I H C—C—C—C—C—C—C—CH —> HC I HC 3
C II CH
3
C2H5
+
4H
c H In PROGRESS IN PETROLEUM TECHNOLOGY; Advances in Chemistry; American Chemical Society: Washington, DC, 1951.
2
McGRATH AND HILL—CATALYTIC REFORMING OF NAPHTHAS
43
Cracking in the presence of hydrogen to form saturated hydrocarbons: n-CnH24 + H2 — > • C3H8 + n-CeHie Isomerization of paraffins: CH
3
H 3 C — C — C — C — C H 3 ^± H C — C — C — C H 3 3
I
H
2
I
H
The pentane fractions produced in the hydroforming process will normally contain approximately 60% isopentanes. Desulfurization :
Downloaded by EAST CAROLINA UNIV on June 19, 2014 | http://pubs.acs.org Publication Date: January 1, 1951 | doi: 10.1021/ba-1951-0005.ch005
C2H5
HC
/ C
Il
II
CH
3
I + Mo + 3 H — > C2H5—C—C2H5 + MoS I 2
HC CH \ / S
H
Thiophene-type sulfur is found in cracked naphthas and is not removed in most gasoline-treating processes, except with very high losses in liquid yield. The extent to which the various reactions occur is a function of operating conditions, feed stock, and condition of catalyst.
The Catalyst In the middle thirties the reactions of naphtha and certain compounds known to be present in naphtha were being studied in university and industrial laboratories. One of the problems was to find a catalyst that was capable of synthesizing an aromatic from a paraffin. It was reasoned that the hydrogenation-dehydrogenation oxide-type catalysts such as molybdenum oxide and chromium might possess suitable activity at temperatures well below those employed in thermal reforming. Table II.
Yield Comparison of Conventional Fixed-Bed Hydroforming with Thermal Reforming Plus Catalytic Polymerization
Feed stock
Mid-continent Heavy Naphtha, 52° A P I Hydroforming Thermal reforming plus catalytic polymerization
Process Yield-quality data Finished gasoline, vol. % R V P , lb./sq. inch C F R M octane (clear) Base octane, C F R M M l . T E L / g a l . to base octane Fuel oil, vol. % Fuel gas (FOE), vol. % Extraneous butanes re quired, vol. % Excess butanes, vol. % a
β
, ,
97.6 70
80.4 75.0
Desulfurization. T h e removal of sulfur compounds from both v i r g i n a n d cracked naphthas has long taxed the ingenuity of petroleum technologists. A t the present time, a number of processes are available for reducing sulfur content and altering the structure of certain classes of sulfur compounds. The change in octane number of the gasoline is invariably slight; however, the responsiveness to tetraethyllead is oftentimes In PROGRESS IN PETROLEUM TECHNOLOGY; Advances in Chemistry; American Chemical Society: Washington, DC, 1951.
McGRATH AND HILL—CATALYTIC REFORMING OF NAPHTHAS
47
improved. Ordinarily, the extent of desulfurization depends on the type and amount of sulfur compounds i n the feed stock, far better percentage sulfur removal being obtained when low-sulfur virgin naphthas are processed. Cracked stocks with appreciable amounts of relatively stable sulfur compounds, particularly of the thiophene type, are attacked but little b y the methods generally employed. 100 h
Δ
07——
Hutings
υ
Downloaded by EAST CAROLINA UNIV on June 19, 2014 | http://pubs.acs.org Publication Date: January 1, 1951 | doi: 10.1021/ba-1951-0005.ch005
+
